A marker-based watershed method for X-ray image segmentation

Digital X-ray images are the most frequent modality for both screening and diagnosis in hospitals. To facilitate subsequent analysis such as quantification and computer aided diagnosis (CAD), it is desirable to exclude image background. A marker-based watershed segmentation method was proposed to segment background of X-ray images. The method consisted of six modules: image preprocessing, gradient computation, marker extraction, watershed segmentation from markers, region merging and background extraction. One hundred clinical direct radiograph X-ray images were used to validate the method. Manual thresholding and multiscale gradient based watershed method were implemented for comparison. The proposed method yielded a dice coefficient of 0.964 ± 0.069, which was better than that of the manual thresholding (0.937 ± 0.119) and that of multiscale gradient based watershed method (0.942 ± 0.098). Special means were adopted to decrease the computational cost, including getting rid of few pixels with highest grayscale via percentile, calculation of gradient magnitude through simple operations, decreasing the number of markers by appropriate thresholding, and merging regions based on simple grayscale statistics. As a result, the processing time was at most 6 s even for a 3072 × 3072 image on a Pentium 4 PC with 2.4 GHz CPU (4 cores) and 2G RAM, which was more than one time faster than that of the multiscale gradient based watershed method. The proposed method could be a potential tool for diagnosis and quantification of X-ray images.     

Parallel watershed transformation algorithms for image segmentation

The watershed transformation is a mid-level operation used in morphological image segmentation. Techniques applied on large images, which must often complete fast, are usually computationally expensive and complex entailing efficient parallel algorithms. Two distributed approaches of the watershed transformation are introduced in this paper. The algorithms survey in a Single Program Multiple Data (SPMD) model both local and global connectivity properties of the morphological gradient of a gray-scale image to label connected components. The sequentiality of the serial algorithm is broken in the parallel versions by exploiting the ordering relation between two neighboring pixels successively incorporated in the same region. Thus, a path is traced, for every unlabeled pixel, down to its region of inclusion (whose label is then propagated backwards); in the second algorithm, regions grow independently around their seeds. In both cases only pixels which satisfy the ordering relation are incorporated in any region. This way, not only different regions are explored in a parallel fashion, but also different parts of the same region, when the latter extends to neighboring subdomains, are treated likewise. Running time and relative speedup evaluated on a Cray T3D parallel computer are used to appreciate the performance of both algorithms.     

OpenCV分水岭算法的改进及其在细胞分割中的应用

分水岭算法是一种基于形态学的图像分割算法,能快速准确地确定连通区域的边界.将基于标记的分水岭算法用于细胞图像的分割,较好地解决了粘连细胞的分割问题.在该细胞分割算法的实现过程中,发现了OpenCV分水岭算法实现的缺陷,通过对相关代码的分析,发现该缺陷存在的原因是算法流程中对相邻像素相对关系的描述存在问题.将OpenCV分水岭算法中对相邻像素取差的绝对值,改为对相邻像素取差值,对该算法进行了改进.实验证明,改进后的OpenCV分水岭算法对细胞图像的分割效果明显好于直接使用OpenCV分水岭算法得到的结果.该方法在不影响分割速度的情况下,提高了OpenCV分水岭算法分割的准确度.     

基于改进分水岭的棉花图像分割方法

针对棉花图像中存在阳光直射和阴影遮挡等因素而导致图像分割精度低、效果差的问题,提出一种改进分水岭的图像分割算法。该方法对原始图像进行各向异性扩散去噪预处理;利用鲁棒中值估计对形态学多尺度梯度图像进行硬阈值法梯度修正;对修正后的图像采用分水岭算法进行分割,对过分割的区域采用基于L*a*b*彩色空间的颜色相似度方案进行区域合并,从而将棉花提取出来。实验结果表明,提出的算法对阳光直射及阴影遮挡等干扰条件下的棉花图像分割能取得较好的效果。     

基于改进分水岭算法的熏烤肉图像分割

针对传统分水岭算法容易产生过度分割的问题,提出一种改进分水岭算法,并用来分割熏烤肉表面颜色.算法先对熏烤肉原始图像作滤波预处理,然后作传统分水岭变换,对产生的过度分割区域,在RGB颜色空间中进行自动种子选取及种子区域生长,最后对剩余小区域进行合并得到分割图像.实验表明,该方法减少了过度分割现象,成功地分割熏烤肉表面颜色,为之后的分析工作奠定了基础.     

基于分水岭算法的尿沉渣图像处理方法研究

医学图像处理是计算机网络和多媒体通信技术在医学上的一项具体应用,已在世界各地得到广泛的重视和应用。尿沉渣显微镜检查是临床检验的一项重要手段,对肾脏疾病的诊断治疗具有十分重要的作用。目前尿沉渣检查多采用显微镜下人工判别。利用计算机技术对临床上尿沉渣图像进行自动分析,将极大提高其临床鉴别的准确性,同时也显著降低临床检查人员的劳动强度。本文利用计算机显微技术对尿沉渣有形成分进行摄取,预处理和特征提取,实现了尿沉渣有形成分自动分割,其分割速度及可重复性都达到了医学临床的要求。     

A high speed roller dung beetles clustering algorithm and its architecture for real-time image segmentation

Applied Intelligence - Several practical applications like disaster detection, remote surveillance, object recognition using remote sensing satellite images, object monitoring and tracking using...     

ITK及其在医学图像分割中的应用

ITK(The Insight Toolkit)是一个开放的、面向对象的类库.它提供了强大的二维医学图像处理功能,主要用于医学图像的预处理、分割及配准.本文主要介绍图像分割的算法以及ITK在图像分割中的应用,并简要介绍一个基于ITK的医学图像处理的实现.     

改进主动轮廓线模型在图像分割中的应用

主动轮廓线模型(Active Contour Model,ACM),也称作蛇(Snake)模型,是一种常用的图像分割算法。在基于主动轮廓线的图像分割中,深度凹陷边界的逼近和弱边界区域的分割一直是一个难点。引入了一种局部纹理模型(Local Profile Model)匹配算法,通过匹配沿控制点法线方向像素和局部纹理模型可以确定弱边界区域的真实边界,并结合一种新的计算控制点曲率外力的算法,使得主动轮廓线模型能够逼近图像的深度凹陷区域的同时提高算法的收敛速度。实验结果表明,该方法是有效的。     

Blobworld: image segmentation using expectation-maximization and its application to image querying

Retrieving images from large and varied collections using image content as a key is a challenging and important problem. We present a new image representation that provides a transformation from the raw pixel data to a small set of image regions that are coherent in color and texture. This "Blobworld" representation is created by clustering pixels in a joint color-texture-position feature space. The segmentation algorithm is fully automatic and has been run on a collection of 10,000 natural images. We describe a system that uses the Blobworld representation to retrieve images from this collection. An important aspect of the system is that the user is allowed to view the internal representation of the submitted image and the query results. Similar systems do not offer the user this view into the workings of the system; consequently, query results from these systems can be inexplicable, despite the availability of knobs for adjusting the similarity metrics. By finding image regions that roughly correspond to objects, we allow querying at the level of objects rather than global image properties. We present results indicating that querying for images using Blobworld produces higher precision than does querying using color and texture histograms of the entire image in cases where the image contains distinctive objects.     

An adaptive unsupervised approach toward pixel clustering and color image segmentation

This paper proposes an adaptive unsupervised scheme that could find diverse applications in pattern recognition as well as in computer vision, particularly in color image segmentation. The algorithm, named Ant Colony-Fuzzy C-means Hybrid Algorithm (AFHA), adaptively clusters image pixels viewed as three dimensional data pieces in the RGB color space. The Ant System (AS) algorithm is applied for intelligent initialization of cluster centroids, which endows clustering with adaptivity. Considering algorithmic efficiency, an ant subsampling step is performed to reduce computational complexity while keeping the clustering performance close to original one. Experimental results have demonstrated AFHA clustering's advantage of smaller distortion and more balanced cluster centroid distribution over FCM with random and uniform initialization. Quantitative comparisons with the X-means algorithm also show that AFHA makes a better pre-segmentation scheme over X-means. We further extend its application to natural image segmentation, taking into account the spatial information and conducting merging steps in the image space. Extensive tests were taken to examine the performance of the proposed scheme. Results indicate that compared with classical segmentation algorithms such as mean shift and normalized cut, our method could generate reasonably good or better image partitioning, which illustrates the method's practical value.     

Improved artificial bee colony algorithm and its application in image threshold segmentation

Multimedia Tools and Applications - Image segmentation is a key problem in the field of computer vision, especially in these fields, such as image processing, analysis and understanding. The key of...     

Automated segmentation of optic disc region on retinal fundus photographs: Comparison of contour modeling and pixel classification methods

The automatic determination of the optic disc area in retinal fundus images can be useful for calculation of the cup-to-disc (CD) ratio in the glaucoma screening. We compared three different methods that employed active contour model (ACM), fuzzy c-mean (FCM) clustering, and artificial neural network (ANN) for the segmentation of the optic disc regions. The results of these methods were evaluated using new databases that included the images captured by different camera systems. The average measures of overlap between the disc regions determined by an ophthalmologist and by using the ACM (0.88 and 0.87 for two test datasets) and ANN (0.88 and 0.89) methods were slightly higher than that by using FCM (0.86 and 0.86) method. These results on the unknown datasets were comparable with those of the resubstitution test; this indicates the generalizability of these methods. The differences in the vertical diameters, which are often used for CD ratio calculation, determined by the proposed methods and based on the ophthalmologist's outlines were even smaller than those in the case of the measure of overlap. The proposed methods can be useful for automatic determination of CD ratios.     

Simplified parameters model of PCNN and its application to image segmentation

Pulse-coupled neural network (PCNN), which simulates the synchronous oscillation phenomenon in the visual cortex of small mammals, has become a useful model for image processing. In the model, several parameters were usually required to properly set for adjusting the behavior of neurons. However, undesired behavior may occur owing to inappropriate parameters setting. To alleviate this problem, we propose to simplify some parameters of PCNN, and apply it into image segmentation. First, exponential delay factors are abandoned for adjusting the neuron input, and the neural input is then associated with image information as well as pulse output. In addition, neural threshold inherent in PCNN is simplified as an adaptive threshold related to image properties, allowing our model to easily alter the behavior of neurons. Particularly, the characteristic of synchronous pulse is thereby kept by introducing a fuzzy clustering method, instead of linking coefficient for grouping pixels with similarity and spatial proximity through iterative computation. Experimental results on synthetic and real infrared images show that the proposed model has high performance of segmentation. Furthermore, our model has better adaptability for segmenting real-world images when compared with several existing PCNN-based methods and some classic segmentation methods.     

A modified support vector machine and its application to image segmentation

Recently, researchers are focusing more on the study of support vector machine (SVM) due to its useful applications in a number of areas, such as pattern recognition, multimedia, image processing and bioinformatics. One of the main research issues is how to improve the efficiency of the original SVM model, while preventing any deterioration of the classification performance of the model. In this paper, we propose a modified SVM based on the properties of support vectors and a pruning strategy to preserve support vectors, while eliminating redundant training vectors at the same time. The experiments on real images show that (1) our proposed approach can reduce the number of input training vectors, while preserving the support vectors, which leads to a significant reduction in the computational cost while attaining similar levels of accuracy. (2)The approach also works well when applied to image segmentation.     

图像分割技术研究与应用

图像分割是指将一副图像分解为若干互不交叠的有意义且具有相同属性的区域。图像分割是数字图像处理中的一项关键技术,其分割的准确性直接影响后续任务的有效性,因此具有十分重要的意义。现有的分割算法在不同程度上取得了一定的成功,但是图像分割的很多问题还远远没有解决,该方面的研究仍然面临很多挑战。文章分析了现有图像分割的各种算法的特点以及存在的问题,对基于图像分割的经典算法进行改进,实现了一种新的分割方法,并将其应用到机器视觉的相关产品当中,取得了良好的效果。     

Color image segmentation with genetic algorithm in a raisin sorting system based on machine vision in variable conditions

This study was undertaken to develop machine vision-based raisin detection technology for various lighting conditions. Supervised color image segmentation using a permutation-coded genetic algorithm (GA) identifying regions in hue–saturation–intensity (HSI) color space (GAHSI) for desired and undesired raisin detection in various conditions was successfully implemented. Images from two extreme intensity lighting and dense conditions: under weak lighting and high-density product and under suitable lighting and low-density product, were mosaicked to explore the possibility of using GAHSI to locate desired raisin and undesired raisin regions in color space when these two extremes were presented simultaneously. The GAHSI results provided evidence for the existence and separability of such regions. In the experiment, GAHSI performance was measured by comparing the GAHSI-segmented image with a corresponding hand-segmented reference image. When compared with cluster analysis-based segmentation results, the GAHSI method showed no significant difference.     

Object density-based image segmentation and its applications in biomedical image analysis

In many applications of medical image analysis, the density of an object is the most important feature for isolating an area of interest (image segmentation). In this research, an object density-based image segmentation methodology is developed, which incorporates intensity-based, edge-based and texture-based segmentation techniques. The proposed method consists of three main stages: preprocessing, object segmentation and final segmentation. Image enhancement, noise reduction and layer-of-interest extraction are several subtasks of preprocessing. Object segmentation utilizes a marker-controlled watershed technique to identify each object of interest (OI) from the background. A marker estimation method is proposed to minimize over-segmentation resulting from the watershed algorithm. Object segmentation provides an accurate density estimation of OI which is used to guide the subsequent segmentation steps. The final stage converts the distribution of OI into textural energy by using fractal dimension analysis. An energy-driven active contour procedure is designed to delineate the area with desired object density. Experimental results show that the proposed method is 98% accurate in segmenting synthetic images. Segmentation of microscopic images and ultrasound images shows the potential utility of the proposed method in different applications of medical image processing.     

Shape "break-and-repair" strategy and its application to automated medical image segmentation

In three-dimensional medical imaging, segmentation of specific anatomy structure is often a preprocessing step for computer-aided detection/diagnosis (CAD) purposes, and its performance has a significant impact on diagnosis of diseases as well as objective quantitative assessment of therapeutic efficacy. However, the existence of various diseases, image noise or artifacts, and individual anatomical variety generally impose a challenge for accurate segmentation of specific structures. To address these problems, a shape analysis strategy termed "break-and-repair" is presented in this study to facilitate automated medical image segmentation. Similar to surface approximation using a limited number of control points, the basic idea is to remove problematic regions and then estimate a smooth and complete surface shape by representing the remaining regions with high fidelity as an implicit function. The innovation of this shape analysis strategy is the capability of solving challenging medical image segmentation problems in a unified framework, regardless of the variability of anatomical structures in question. In our implementation, principal curvature analysis is used to identify and remove the problematic regions and radial basis function (RBF) based implicit surface fitting is used to achieve a closed (or complete) surface boundary. The feasibility and performance of this strategy are demonstrated by applying it to automated segmentation of two completely different anatomical structures depicted on CT examinations, namely human lungs and pulmonary nodules. Our quantitative experiments on a large number of clinical CT examinations collected from different sources demonstrate the accuracy, robustness, and generality of the shape "break-and-repair" strategy in medical image segmentation.